1. Field of the Invention
This invention pertains to human ventilatory measurement instruments. More particularly, it concerns a portable hand-held spirometer for measuring pulmonary function and reporting the results as a plurality of lung function parameters.
2. Description of the Prior Art
A spirometer is a form of spiro analyzer or ventilometer and is generally defined as an instrument for measuring the breathing capacity and other bronchial activity of the lungs. Spirometers find wide utilization in the diagnosis of lung and breathing difficulties such as emphysema, asthma and chronic bronchitis. More particularly, they have found use in monitoring the progress of recipients of lung transplants. Ordinarily, spirometers involve large equipment located in laboratories or doctors' offices. The testing requires the patient to breath into the equipment with a forced expiration.
The parameters obtained through the use of spirometers are reported in well-accepted formats such as "forced vital capacity" (FVC) which is the volume of air that is exhaled following a maximum single breath regardless of the time taken; "peak expiratory flow" (PEF) which is a measure of the highest flow rate of air from the lungs during a single forced expiration; "forced expired volume during the first second" (FEV.sub.1) which represents the volume of air that can be exhaled forcibly in one second; "FEF.sub.25/75 " which is the average expiratory flow for the middle 50% of the expiration; and, other combinations of these values such as FEV.sub.1 expressed as a percentage of the FVC. Depending upon the particular malady involving the lungs, the physician or physiotherapist may choose to look at one, some, all of these parameters, or other ones.
Large electronic spirometers situated in a laboratory or doctor's office are often massive and quite expensive and therefore not installed at many locations, thereby requiring the patient to travel substantial distances to undergo the testing. There are some small, hand-held, portable meters presently available, however, they measure only peak flow. There are also some portable electronic spirometers available, however, they measure only a few parameters of lung function and their cost is such that few, if any, individuals can afford them for home monitoring. Further, because of the lack of multiple parameter reporting, the treating physician is often left with only partial results which deprive him or her of a more complete analysis of the patient's lung condition.
Some of these units require the patient to record the results of the tests and bring them to the physician's office for later analysis. This practice can result in errors in recording and evaluating the data. Accordingly, there exists in the spirometer field, a significant and continuing need for a portable spirometer that measures many or all of the desired parameters, priced to be economically affordable by most patients, and that would automatically record the results for reporting to the user or to the physician's office for analysis.